The Molecular Diagnostic Core is a new service in the Program Project. Its major function will be the "realtime" molecular staging of histopathology (-) sentinel lymph nodes (SLN) of MSLT II patients. To accomplish this major task, the Core will be responsible for procurement, processing, purifying, quantifying, cryopreserving, as well as performing multimarker quantitative realtime RT-PCR assays on these paraffin-embedded (PE) SLN. The results will be immediately used by Core C to enter patients in the randomization for complete lymph node dissection (CLND) or routine follow up in MSLT II. The Core's other important functions will be procurement and isolation of RNA from PE SLN, non-SLN and primary tumor from JWCI, MSLT I & II for Project 0003. The main objective is to provide a centralized facility for procurement, processing, and storage of RNA and DNA from archival PE specimens. The MSLT I & II are an invaluable resource for procurement of archival tissues for this proposal and future studies. To ensure the integrity of samples and the meaningfulness of analysis, it is crucial that there is centralization of the operation so that stringent standard operating procedures (SOPs) of specimen handling, processing, cryostorage, and cataloging can be implemented. Prospectively collected blood from patients entered in the MSLT II will be used for isolating circulating tumor DNA in serum for Project 0003. Another major task of the Core will be to produce recombinant melanoma-associated antigen (MAA) proteins to be used in a MAA specific ELISA in Project 0001. The Core will function as the center for these multiple task operations.